Electrochemical measurement is capable of performing high-sensitivity measurement with use of relatively simple apparatus configurations and is frequently used in the field of analytical chemistry. Available electrochemical measurement schemes include potentiometry, amperometry, voltammetry, and impedance measurement, and further include other detection methods such as methods for detecting photons by combinatorial use of these with an optical element or the like, for example.
Generally, an electrode used for electrochemical measurement is frequently made of a platinum group metal—especially, platinum—in the light of its excellent chemical stability characteristics. In recent years, also in the analysis of chemical components contained in liquid samples such as blood and urine, platinum is used as the electrode to be built in a flow cell.
For example, Patent Literature 1 discloses that in the case of continuous measurement of a chemical component in blood or urine repetitive measurement is enabled through a process of applying a plurality of electrical potentials between a working electrode and a counter electrode on a per-analysis basis, in addition to cleaning and main measurement.
An example using a mixture material of platinum and metal oxide as the electrode is found in Patent Literature 2, which discloses therein an electrode comprising a surface layer formed on the surface of a metallic base substance by solid solution of tin oxide and antimony oxide and a mixture layer of a platinum-group metal or its oxide and an oxide of IV- or V-group metal as an intermediate layer between the metal base substance and the surface layer. Additionally, Patent Literature 3 discloses an electrode for electrolysis having an outer layer above a surface of a titanium or a titanium alloy body with an intermediate layer being laid therebetween, wherein the outer layer is made of a mixed metal oxide comprising iridium oxide, platinum, and at least one kind of metal oxide selected from the group consisting of niobium oxide, tantalum oxide, and zirconium oxide.
Patent Literature 4 discloses therein an oxygen sensor's electrode comprising either an oxide semiconductor or a solid electrolyte, the surface of which is coated with an electrode material containing an oxide of aforementioned the aforementioned constituent metal and platinum.
Concerning the electrode material containing a platinum-group metal, Patent Literature 5 describes therein use of a platinum-group metal for the counter electrode and the working electrode. Additionally, Patent Literature 6 discloses an electrode for electrochemical reaction which is composed with a valve metal such as titanium, tantalum, or zirconium and platinum by thermal pressing, and also discloses a manufacturing method of the electrode.
Furthermore, Patent Literature 7 discloses an electrode with sequential formation of a platinum alloy coat layer and a coat layer made of iridium oxide and/or platinum oxide on a titanium, niobium, or tantalum base material, as an electrode for electrolyzing a salt solution to produce strongly acidic water having bactericidal action and an insoluble electrode used for certain applications such as electrolytic cleaning treatment of waste water containing organic substances.